1. Field of the Invention
This invention relates to pharmaceutical compositions and more particularly to controlled release pharmaceutical compositions containing hollow tube drug delivery systems.
2. Prior Art
Controlled delivery or sustained release formulations have gained wide popularity in the pharmaceutical industry. The popularity of these formulations has grown due to the usefulness in extending the utility of particular drugs which require specific dosages and delivery of the dosage at a non-toxicological rate.
In the pharmaceutical industry, sustained release has been used extensively for oral medications over a number of years. Sustained release formulations include encapsulated pellets or beads, enteric coated formulations, use of slightly soluble salts, drug complexes, and porous tablets containing dispersed drugs.
Controlled drug delivery on the other hand is aimed at achieving sustained release of a drug at a constant rate (zero order) for long periods of time. Zero order release can be provided at the present time only by mechanical pumps, such as automatic syringes and implantable pumps, osmotic pumps such as Alza's systems known as Alzet.RTM., Progestasert.RTM. and Ocusert.RTM., chemically controlled biodegradable mechanisms, and diffusional systems based on polymeric membranes and matrices such as the currently marketed transdermal systems for the delivery of nitroglycerin for angina pectoris and scopolamine for motion sickness.
Solid fibers have been used in sutures encapsulated with antibiotics and in intrauterine devices to release hormones.
While much work has been done over many years relating to the sustained release and the controlled release of drugs, there still is a need for new systems that are capable of delivering a predetermined amount of a drug at a predetermined rate, over a selected time. The present invention provides such systems.